Doman

On the menu screen, type the following:

puszczabukowa     Second level
starygrzyb        Third level
ciemnajaskinia    Fourth level
zamekzabytek      Fifth level
kochamzabijanie   Immortality
jezusmoimpanem    Weak enemies
sramnapc          12 lives
kalasznikov       Machine gun
jezuszabijaka     Kill enemy with crossbow in one shot
szczecinrulez     7 credits
drewnopc          Better enemies
uczciwy           Clear all cheat codes